斑点叉尾鮰源嗜麦芽寡养单胞菌胞外蛋白酶的纯化及性质研究

Purification and characterization of extracellular protease of Stenotrophomonas maltophilia isolated from Ictalurus punctatus

采用硫酸铵盐析,DEAE Sephadex A-50凝胶层析等方法从嗜麦芽寡养单胞菌胞外产物中提纯了一种分子量为45.7ku的单一多肽蛋白酶。该酶对小鼠和斑点叉尾鮰具有明显的致死作用,其LD50分别为4.33μg.g-1体重和3.49μg.g-1体重。酶的最适温度为20℃,热稳定性差,100℃作用15min酶活完全丧失,最适pH为9.0,PMSF对酶活无影响,部分金属离子如Ca2+、Hg2+、Cu2+能使酶活性明显下降,而Co2+对酶有一定程度的激活作用,EDTA能完全抑制酶活性,表明该酶为一种金属蛋白酶。

A stain of Stenotrophomonas maltophilia was isolated from the diseased Ictalurus punctatus of a fishfarm in Sichuan province, and an extracellular pmtease was partially purified from the culture solution of the S. maltophilia by ammonium sulfate and DEAE Sephadex A-50 fast flow. The result showed that the molecular weight of the purified protease from Ictalurus punctatus by SDS-PAGE was 45.7 ku. The purified protease was injected to rats and Ictalurus punctatus intraperitoneally. It resulted in heavy fatalities. The LD50 of exWacellular protease to rats and Ictalurus punctatus were 4.33 μg·g^-1 and 3.49μg·g^-1respectively. It showed that the optimal temperature was 20℃ and the optimal pH was 9.0. PMSF couldn＇ t affect the activity but EDTA, Ca^2 ＋, Hg^2 ＋, Cu^2 ＋ could reduce the activity of protease greatly. However, Co^2＋ could enhance the activity. It demonstrated that the protease was a metal-protease.